1991 Chevy Corsica car goes on and off while driving

hi, well my car goes on in the morning and starts to shake when i turn it on. when i am driving the car the car turns off all of a sudden. sometimes it turns off and some times it doesn't i already changed the map sensor the oxygen sensor, 2 other sensors, and the fuel filter. and it still turns off when i'm driving it.. ive taken it to 3 different mechanics and they just charge me and can't fix it..thank you